Yesterday while trading messages with a friend we discussed my previous post about columns disappearing. He suspected it might explain the issue he was observing. After looking more closely it turned out that it doesn't. In his situation the structural columns were modeled the full height of the building and Join Geometry was used on walls, that passed through (overlapped) the columns, at each floor (level). The result: at some levels no column appeared while at others they do.
It was necessary to pull the walls back so they stop at the surface of the columns. Join Geometry allowed for the desired appearance and the columns reappeared at the other levels where they were missing earlier.